NEW YORK, March 31 (Reuters) - A California nut grower and processor issued a nationwide recall of pistachios on Tuesday due to possible salmonella contamination, and authorities said consumers should avoid all pistachio products until more information was available.

The U.S. Food and Drug Administration (FDA) said several illnesses had been reported that may be associated with the contaminated pistachios. The FDA said it and the California Department of Public Health were investigating the matter.

The FDA said it first learned of the problem on March 24, when Kraft Foods Inc KFT.N informed the agency that Back To Nature trail mix was contaminated. Kraft had identified the source of the contamination as Setton.

Salmonella can cause serious and sometimes fatal infections in young children, frail or elderly people, and others with weakened immune systems.

The recalled nuts were shipped on or after Sept. 1, 2008, by Setton Pistachio of Terra Bella Inc. The FDA said the recall would likely include many products in which pistachios were used as ingredients.

Last week, Kraft recalled Back To Nature Nantucket Blend trail mix containing pistachio nuts [ID:nPnCG88836], and grocery chain Kroger Co (KR.N) recalled its Private Selection shelled pistachios, which are sold at its various chains. [ID:nPnCL90405]

Kraft said on Tuesday that it was recalling almost two dozen products under the Planters and Back to Nature brands supplied by Setton after Sept. 1.

A spokeswoman for Wal-Mart said that although the retailer had been assured by Setton that its Sam's Choice pistachios were not part of the recall, Wal-Mart was taking them off its shelves in an "abundance of caution" after talking to the FDA.

Supervalu Inc (SVU.N), which owns Albertsons, Jewel-Osco and other food store chains, said it was removing all pistachios and products containing them from its stores until it gets more information about specific products being recalled.

The pistachio contamination is not connected to the recent salmonella outbreak involving peanuts and peanut butter.

Pistachios are not consumed as widely in the United States as peanuts, but are often used in such products as ice cream and in Middle Eastern desserts such as baklava.

Setton's recall involves more than 2 million pounds of pistachios, according to a spokeswoman for the company.

Diamond Foods Inc DMND.O, which sells Diamond brand cooking nuts and Emerald brand snacking nuts, said it does not buy any nuts from Setton and does not believe any of its products are affected.

CVS Caremark Corp (CVS.N) and Walgreen Co WAG.N said none of their private branded products were affected by the recall. (Reporting by Martinne Geller; Additional reporting by Jessica Wohl and Brad Dorfman in Chicago, Nicole Maestri in New York and Amitha Rajan in Bangalore; Editing by Gerald E. McCormick, Dave Zimmerman, Toni Reinhold)